1. Field of the Invention
The present invention relates to a method and an apparatus for extruding ceramic multi-layer structures, in which integral ceramic multi-layer structural bodies can be obtained by a single extrusion step from molding ceramic compounds having different compositions, grain sizes, color tones, etc.
2. Related Art Statement
Conventionally, two-layer structural bodies in which ceramics having different properties such as different compositions, grain sizes, water contents, viscosities, color tones, porosities, etc. are laminated in the form of two layers are employed for various uses.
These multi-layer structural bodies are each integrally produced by forming a ceramic shaped body as a base layer, and then coating another ceramic layer on the ceramic shaped body. For instance, in order to produce a cylindrical two-layer structural body, a cylindrical ceramic shaped body is extruded or compression-molded as a base, and then another layer is formed on the thus shaped cylindrical ceramic body by dipping, brushing, or spraying a ceramic slurry.
For this purpose, at least two steps are employed: an extrusion step or a compression molding step and a coating step are required to produce ceramic two-layer structural bodies, so that the number of the steps unfavorably increases. In addition, it is impossible to easily control the thickness of a coated layer in the coating step and a mixing state of a boundary layer. Furthermore, it is difficult to form a ceramic thin layer with a high viscosity slurry by dipping, brushing or spraying.